Tentative implementation of string slices (hidden under the flag --string-slices).

src/regexp-macro-assembler.cc

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 102 matching lines @@
   ASSERT(previous_index >= 0);
   ASSERT(previous_index <= subject->length());
 
   // No allocations before calling the regexp, but we can't use
   // AssertNoAllocation, since regexps might be preempted, and another thread
   // might do allocation anyway.
 
   String* subject_ptr = *subject;
   // Character offsets into string.
   int start_offset = previous_index;
-  int end_offset = subject_ptr->length();
+  int char_length = subject_ptr->length() - start_offset;
+  int slice_offset = 0;
 
-  // The string has been flattened, so it it is a cons string it contains the
+  // The string has been flattened, so if it is a cons string it contains the
   // full string in the first part.
   if (StringShape(subject_ptr).IsCons()) {
     ASSERT_EQ(0, ConsString::cast(subject_ptr)->second()->length());
     subject_ptr = ConsString::cast(subject_ptr)->first();
+  } else if (StringShape(subject_ptr).IsSliced()) {
+    SlicedString* slice = SlicedString::cast(subject_ptr);
+    subject_ptr = slice->parent();
+    slice_offset = slice->offset();
+    ASSERT(slice->parent()->IsSeqString());

[Vitaly Repeshko, 2011/08/12 19:01:00]

Should this be here? Looks like we can handle external strings fine below.

   }
   // Ensure that an underlying string has the same ascii-ness.
   bool is_ascii = subject_ptr->IsAsciiRepresentation();
   ASSERT(subject_ptr->IsExternalString() || subject_ptr->IsSeqString());
   // String is now either Sequential or External
   int char_size_shift = is_ascii ? 0 : 1;
-  int char_length = end_offset - start_offset;
 
   const byte* input_start =
-      StringCharacterPosition(subject_ptr, start_offset);
+      StringCharacterPosition(subject_ptr, start_offset + slice_offset);
   int byte_length = char_length << char_size_shift;
   const byte* input_end = input_start + byte_length;
   Result res = Execute(*regexp_code,
-                       subject_ptr,
+                       *subject,
                        start_offset,
                        input_start,
                        input_end,
                        offsets_vector,
                        isolate);
   return res;
 }
 
 
 NativeRegExpMacroAssembler::Result NativeRegExpMacroAssembler::Execute(
     Code* code,
-    String* input,
+    String* input,  // This needs to be the unpacked (sliced, cons) string.
     int start_offset,
     const byte* input_start,
     const byte* input_end,
     int* output,
     Isolate* isolate) {
   ASSERT(isolate == Isolate::Current());
   // Ensure that the minimum stack has been allocated.
   RegExpStackScope stack_scope(isolate);
   Address stack_base = stack_scope.stack()->stack_base();
 
@@ skipping 92 matching lines @@
     return NULL;
   }
   *stack_base = new_stack_base;
   intptr_t stack_content_size = old_stack_base - stack_pointer;
   return new_stack_base - stack_content_size;
 }
 
 #endif  // V8_INTERPRETED_REGEXP
 
 } }  // namespace v8::internal